I think it is a natural idea to start the lead where the bumper ends for a uniform distribution of weight around the hoop. But ofcourse you can also do otherwise. It mimics the weight distribution of a bumperless or CAP'ed racket.

But the weird thing is that adding lead at that place will move the SS down in the stringbed, towards the throat of the racquet. Matbe Djokovic felt that he needed lead there because he was making ball contact close to his body.

^^ A 1/2 would make the most sense. I would assume his hands are massive given his height.

Click to expand...

Yup. Probably so... but it's still preference, and his preferences might have changed...or Nate might have rushed in the interview...or whatever.
Found the other reference...where he mentions the 4 1/2 (#4)

His lead tape/configuration changed since then as well since there was no visible lead on that racquet...it was somewhere under the bumper...and now it is very visible @ 3 + 9 and below...and done by the Head pro room as per the latest video posted in this thread.